Question

how are gaseous fuels better than liquid and solid in terms of efficiency

Answer 1

Answer:

consume less space and gas molecules have big distance between them than solid and liquid

Answer 2

Solids conduct heat better than liquids, which are in turn better conductors than gases. The particles in a solid are most tightly bond and their positions are more or less fixed relative to each other (Fig. 5a). The force between adjacent particles is strong, making heat transfer by collision the most efficient.